Potassium, Na+,K+-pumps and fatigue in rat muscle
Potassium, Na+,K+-pumps and fatigue in rat muscle
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DOI：
10.1113/jphysiol.2007.136044
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发表时间：
2007-10-01
影响因子：
5.5
通讯作者：
Nielsen, Ole Baekgaard
中科院分区：
文献类型：
--
作者：
Clausen, Torben;Nielsen, Ole Baekgaard
在收缩活动中，骨骼肌经历了胞浆K+向间质间隙的净损失。在大强度运动中，人体动脉血中的血浆K+可达8 mM，间质K+可达10-12 mM。这会导致去极化、兴奋性和收缩力的丧失。然而，这些细胞外K+([K+](O))的生理性增加对收缩耐力的影响还知之甚少。将4周龄大鼠比目鱼肌置于换能器上，在含4~10 mMK+的Krebs-Ringer碳酸氢盐缓冲液中等长收缩，通过记录60 Hz连续刺激时力量衰减率来评估耐力。[K+](O)从4 mm增加到8 mm或10 mm，平衡肌肉40或20分钟，力量下降的速度分别增加2.4%和7.2%(P<；0.001)。通过细胞内Na+负荷、β(2)激动剂沙丁胺醇、肾上腺素、降钙素基因相关肽、胰岛素或重复兴奋刺激Na+、K+泵，可明显减轻或显著降低8 mM或10 mM K+引起的耐力下降。总之，兴奋引起的[K+](O)升高是高频疲劳的一个重要原因，而Na+，K+泵对于维持[K+](O)的生理范围内的收缩是必不可少的。在8-10mMK+连续刺激时的收缩记录可用来分析影响工作的离体肌兴奋性的药剂或条件的影响。
During contractile activity, skeletal muscles undergo a net loss of cytoplasmic K+ to the interstitial space. During intense exercise, plasma K+ in human arterial blood may reach 8 mM, and interstitial K+ 10-12 mM. This leads to depolarization, loss of excitability and contractile force. However, little is known about the effects of these physiological increases in extracellular K+ ([K+](o)) on contractile endurance. Soleus muscles from 4-week-old rats were mounted on transducers for isometric contractions in Krebs-Ringer bicarbonate buffer containing 4-10 mM K+, and endurance assessed by recording the rate of force decline during continuous stimulation at 60 Hz. Increasing [K+](o) from 4 to 8 or 10 mM and equilibrating the muscles for 40 or 20 min augmented the rate of force decline 2.4-fold and 7.2-fold, respectively (P < 0.001). The marked loss of endurance elicited by exposure to 8 or 10 mM K+ was alleviated or significantly reduced by stimulating the Na+,K+-pumps by intracellular Na+ loading, the beta(2)-agonist salbutamol, adrenaline, calcitonin gene related peptide, insulin or repeated excitation. In conclusion, excitation-induced increase in [K+](o) is an important cause of high-frequency fatigue, and the Na+,K+-pumps are essential for the maintenance of contractile force in the physiological range of [K+](o). Recordings of contractile force during continuous stimulation at 8-10 mM K+ may be used to analyse the effects of agents or conditions influencing the excitability of working isolated muscles.